Characteristics of different underwater imaging systems are compared based on the results of Monte Carlo simulations of light transport in the sea water. The consideration includes systems with continuous-wave illumination, modulated illumination, pulsed systems with time gating detection, and hybrid systems with probing pulse modulated at high frequency. To generalize the study, the ratio of SNRs of different systems when imaging a sinusoidal test pattern is analyzed. Pulsed systems are demonstrated to provide higher SNR as compared to continuous-wave systems for typical imaging distances varying in the range 35-60 m, while systems with modulated illumination provide a SNR comparable to that for continuous-wave systems. Hybrid systems provide SNRs comparable to that in pulsed systems benefiting, however, from higher contrast transfer coefficient.